Acquired stuttering: a motor programming disorder?

Acquired stuttering (AS) can follow unilateral right, left or bilateral hemispheric lesion, and can, but not necessarily, coexist with aphasia. In this paper we experimentally tested motor programming skills in a patient with AS of vascular origin. Motor programming consists in the structuration of the whole sequence of response prior to the onset of the first response element of a sequence of responses. Chronometric studies have shown that the time to initiate a sequence of manual responses is a function of the characteristics of the forthcoming sequence of responses. In our patient, reaction times involving single motor responses performed by right hand were within normal limit. On the contrary, when the task required a sequence of motor responses, there was a consistent difficulty in following the sequence: moreover, in the few correct sequences, reaction time analysis showed a lack of motor programming. It is suggested that AS could be the speech epiphenomenon of a more generalized disturbance of motor programming.